Acoustic device



C. KYLE ACOUSTIC DEVICE Feb. 4, 1930.

Filed Maron 12. 192e IIIIIIIII'II- liPatented Feb. 4, 1,930

conm KYLE, or su JOSE, cALmonmA,

UNITED nEPnonUcEns PATENTS coarom'rron,

:common E NEVADA 'ASSIGNOIEt, BY MESNE ASSIGNMENTS, TO

F S'I.` CHARLES, ILLINOIS, A COR- Aeous'rrc DEVICE Application led March12,1928. Serial No. 260,832.'

This invention relates to an electrostatic acoustic device fortransmitting and receiving purposes, as in radio broadcasting andreceiving, etc. It is known that true sound reproduction,

free from disturbing resonant notes and" distortions, is best obtainedby means of apparatus working on an electrostatic or con.

- denser principle. An electrostatic transmitter or reproducer -usuallyconsists of a rigld plate and a flexible plate, the latter serving las adiaphragm.4 The diaphragm andthe plate are placed as closely'togetheras'possible, as the etliciency is in direct' ratio to 15 the square ofthe distance or spacing'maintained between the same. While anelectrostatic or condenser ,type of acoustic device is fairlysatisfactory, there are objections, as a considerable spacing must bemaintained, usually'a sixty-fourth of an inch or more, i. e., flexing orbending of the diaphragm when struck by sound waves or when electricallyactuated, will otherwise 4permit the plates to contact. Also due to theflexing of the diaphragm, devices of this character are fairly limitedin size. For instance, the averagecondenser or electrostatic microphoneas used is seldom `over three inches inA diameter and as such is notideal for low frequency sound-wave transmission or reproduction, nor aredevices of this character altogether suitable as receivers or loudspeakers, as the area presented is too smallor proper air coupling.

thin; to provide a structure which permits` close spacing between thediaphragm and the plate; to provide a structure which permits divisionof a large 'area diaphragm into a number of cooperating diaphragms ofcomparatively small-area; and further, toA pro'- vide a-structure whichpermits rigid clampof the diaphragm tomaintain uniform .3, but they areconsiderably larger in diameter than the holes 2. C indicates the dia-VThe object of 'the present invention is to" generally improve andsimplify the construcspacing and to prevent mechanical vibrations, etc.l

The invention is shown, by way of illustration, inthe accompanyingdrawings, in which:

Figure 1 is a planview of a portion of the acoustic device, said viewbeing broken away to show the rigid and the exible plates,lthe

insulating medium and the clamping plate,

Figure 2- is an enlarged transverse cross- 60 section of a portion ofthe acoustic device,

Figure 3 is a partial section showing a ximodified. form of thestructure.

Referring to the drawings in detail, A in-l dicates a rigid plate whichis providedwith v a plurality of holes or perforations, such asindicated at 2. B indicates a plate constructed of a,dielectricmaterial. This plate is also provided with holes orperforations phragm plate which is thin and iexible. Itl

ris disposed on top of the dielectric plate B and is rigidly clamped orsecured thereto by means of a clamping plate D. This plate is alsoprovided with holes or perforations such as indicated at 4, theperforations being of a size substantially the same as the holes 3formed in the dielectric plate.

The plate A may 'be constructed of any metal desired. For instance,steel, brass, copper, aluminum, etc., and it should be fairly thick orheavy so-as -to prevent vibra-tion;l thereof when the acousticdevice isin opera- The plate C is also constructed of metal, such as steel,brass, aluminum, etc., but it should be asthin as possible as it must beable to iiex or bend when struck by vsound waves, as when used as atransmitter or when' electrostatically attracted b the plate A, when itis used as a repro ucer or a loud speaker Thin shim metal or leaf metal,such as gold leaf, aluminum leaf, etc. may be employed. The flexibleplate C is unperforated and as 'such covers the perforations 2 and 3formed-inthe respective plates A and B, and as the perforations 3 arecomparatively large a diaphragm is formed over yeach set of The spacingmaintained between lthe flexible plate C andthe rigidplate A should bethe spacing between them must accordingly be sufficient to preventcontact when the device is in operation. The spacing will, -accordingly,be in proportion to the diameter of the holes 3, and in few instanceswill eX- ceed 3/1000 of an inch.

. The plate'D merely serves as a clamping late to secure the diaphragm Cand the dielectric plate B in rigid contact with the plate A. Bolts suchas indicated at 5 may be employed, these bolts extending through theplates A, B, C and D, and insulating t sleeves and washers may beemployed as indicated at 6 to prevent short-circuiting of the plates..The plate D may be constructed of any material desired, the materialemployed be1ng of no importance as long as the'plates A and C areinsulated with relation to eachother. The bolts may be placed atstaggered intervals as shown in Figure 1, and any suitablenumber may beemployed. The holes 4 formed in the clampingplate are preferably of thesame diameter as the holes 3 in the dielectric plate B. This to insure arigid support for the diaphragm'and also to provide as large a couplingarea as possible between the movable portions of the diaphragm and theair.

The device so constructed is ready for use and may be connected with anytransmitting or receiving radio set or in any electric circuit wheresound is to. be transmitted or received. When usedas a loud speaker in aradio receiving set, it is preferable to employ po'wei` amplification inthe audio frequency side of the circuit 5 the two terminals leading fromthe audio frequency amplifying power circuit being connected, one withthe plate A and one with the diaphragm C. A modulated or varying currentpotential is in this manner applied to the two plates, and electrostaticattraction, varying according to the degree of applied potential, willcause movement of the flexible belt or diaphragm with relation to therigid plate, and

as the diaphragm makes a -direct coupling with the surroundingatmosphere, sound or acoustic vibrations will result.I The manner ofconnecting an electrostaticl device of this character in a transmittingcircuit is well known, and a detailed description thereof should beunnecessary.

An electrostatic speaker constructed as here illustrated is highlyefficient, as an exceedingly small spacing may be maintained between therigid and the flexible plates. A thin diaphragm or plate may beemployed, which may be constructed of leaf metal, shim metal, or thelike, and faithful `tone reproduction is accordingly the result, as suchdiaphragms have comparatively little weight or inertia of their own, andfurthermore are sensitive both to high and low soundwave frequencies.The device may be constructed so large as to present an air couplingequal to several square feet. In fact, limits, as far as area isconcerned, is unrestricted. Mechanical rattles, buzzing, and' other tonedistortions are avoided, as the structure is exceedingly rigid andsubstantial and free of vibratin T periods of its own.

If a flexible unperforated diaphragm is employed, such as shown in myPatent No.l 1,644,387, issued October 4, 1 927 land entitled Acousticdevice, a clamping plate such as indicated at' F in Figure 3 may beemployed to advantage. I n this modification indicates the rigidperforated plate, H the VfieX- ible diaphragm, and J the flexibleconductor.

The perforated plate G is in this instance upreferably punched in such amanner that raised surfaces 17 are formed around each hole orperforation. The diaphragm H rests on the raised surfaces and isslightly elevated or raised with relation to the sloping surfacesindicated -at 18. formed in the clamping plate as indicated at 19, arelarger in diameter than the perforations in the plate G. The solidportions of The perforations the clamping plate, indicated at20,'willthus only engage the high spots 17 of the Aplate G and thediaphragm and the flexible conductor will be rigidly clamped tothesepoints with relation to the rigid plate, while the remaining portions ofthe diaphragm and the flexible conductor will'be free to vibrate. Thisclamping of portions of the diaphragm and the flexible conductor isimportant when certain diaphragm materials are employed, for instance,paper, mica, celluloid and similar materials present a hard surface tothe rigid plate G and as such have a tendency to buzz or rattle, butwhere materials of this character are rigidly clamped where the highspotsareencountered, rattling or buzzing is v substantially eliminated.

- While certainfeatures of the presentinvention have been more or lessspecifically illustrated and described, I wish it understoodV thatvarious changes may be resorted to within the scope of the appendedclaims; similarly, that the materials and finishes of the several parts.employed may be such as the manufacturer may decide or varyingconditions or uses may demand. v

Having thus described my invention, what I claim and desire to secure byLettersv Pat-` ent is:

1. Anacoustic' device comprising a perforated plate, dielectricperforated plate diS- posed in contact therewith, the perforations inthe dielectric plate being larger than the perforations'in thefirst-named plate and concentric therewith, and a flexible' conductorcovering the dielectric plate and forming a diaphragm.v

2. An acoustic' device comprising a' perforated plate, a dielectricperforated plate disposed in contact therewith, the perforations in thedielectric plate being larger than the perforations inthe first-namedplate and concentric therewith, a flexibleconductorcoveringlthe.dielectricplate and forming a diaphragm, anda clampingplate engaging the diaphragm and maintaining it in contact with thedielectric'plate. f

3'. An acoustic Adevice comprising a perforated plate, agilielectricperforated plate disposed in contact therewith, the perforationsfin-thedielectric plate being larger .than the perforationspin the first-namedplate and concentric therewith, a flexible conductor covering thedielectric plate and formingadiaphragm, and a clamping plate engagingthe diaphragm and maintaining it in contact with the dielectric plate,said clamping plate having perforations formed therein lsubstantiallyofy the same size as the perforations in the dielectric plate andaligning therewith.

' .4. An acoustic devicecomprising a dielectric perforated plate, aperforated conductor plate disposed on one side, a flexible conductorplate disposed on the opposite side and forming a1` diaphragm, Aandmeans clamping all ofthe plates together and maintaining the platesinrigid contact with relation lto each other.v Y

V"5. An acoustic device comprising a`rigid erforated conductor plate, aflexible conductorjplate'forming a diaphragm, a, dielectric plateinterposed between the rigid plate and the diaphragm plate, saiddielectric plate being perforated and the perforations being larger thanthe perforations in the rigid plate and being concentric therewith so asto leave `an exposed surfacearound each perforation in the rigid plate.

device comprising a rigid perforated conductor plate, a flexibleconductor plate forming a diapliragni,l a dielectric plate interposedbetween the rigid plate and Vthe diaphragm plate, said dielectric platebeing perforated and the perforationsl being larger than theperforations in the rigid plate "and being concentric therewith so as toleave an exposed surface around each perforation diaphragm, and a,clamping plate engaging the 'flexible conductor, said clamping platehaving perforations formed therein which are larger in diameter than theperforations-in the rigid plate.

- 8. An acoustic device comprising a rigid plate, meansfor providing aplurality of high points on the plate, said plate having perforationsformed thereinintermediate the lhigh points, a flexible diaphragm placedin contact with the high points of the rigid plate,-

.perforated plate, a flexible diaphragm covering the plate, a flexibleconductor covering the diaphragm,l and a clamping .plateengaging theflexible conductor. and exerting pressure on theconductor and thediaphragm so as to maintain them in rigid Contact with the.

rigid plate.

10. An acoustic device comprising a rigid perforated plate, a flexiblediaphragm covering the plate, a flexible conductor covering thediaphragm, and a foraminated clamping plate engaging the flexibleconductor and exerting pressure on the conductor and the diaphragm so asto maintain them in rigid contact with the rigid plate. v

'COLIN KYLE in the rigid plate, said dielectrcplate maintaining a fixeds acing between portions of the diaphragm p ate and the rigid plateandmeans clamping the plates together.

7. An acoustic device comprising a rigid perforated plate, a'flexiblediaphragm covering the plate, a flexible conductor covering the

